Computer simulated dissolution of carbide precipitates in alloys

Conventional theory on the dissolution of a spherical particle of a second phase in an alloy is shown to be inappropriate when considering carbide species. In particular, the assumptions of an error function solute concentration profile and a constant equilibrium solute concentration level at the interface cannot be made. A model for computer simulated dissolution is therefore proposed which is based on the diffusion of solute away from a carbide particle across discrete shell increments. The method is used to predict times for complete and partial dissolutions of M23C6 particles in Nimonic 80A (registered trade mark of Henry Wiggin and Co. Ltd). As a result, the effect of solution heat treatment of the alloy is more clearly understood and practical improvements are recommended.